Display screen or portion thereof with a graphical user interface of a mobile device



FIG. 1 is a front view of a first embodiment of a display screen with agraphical user interface of a mobile device; and,

FIG. 2 is a front view of a second embodiment of a display screen with agraphical user interface of a mobile device.

The broken line showing a display screen and user interface elements isfor the purpose of illustrating portions of the article and forms nopart of the claim.

CLAIM The ornamental design for a display screen or portion thereof witha graphical user interface of a mobile device, as shown and described.